Pneumatic or hydraulic pressure sensors with several thresholds of response

Abstract

The present invention relates to an improvement in pneumatic or hydraulic pressure sensors with several thresholds of response. There often is a need for pressure sensors with several thresholds of response to predetermined pressure values. One such case exists with washing machines wherein loads at predetermined levels are required. The pressure sensor must therefore signal on the basis of the hydrostatic pressure the level of leading of the washing tub for the closing of, for example, an electric valve. According to the present invention, the pressure sensor provides for a "lung" comprising an elastic membrane exposed to pressure, which acts on an element that operates a group of electromechanical switching elements, each of which is sensitive to a preestablished actuating force corresponding in turn to a given response pressure of the pressure sensor.

I claim: 
     
       1. A pressure sensing device having a plurality of thresholds of response comprising a membrane movable in response to pressure applied thereto,   an actuator movable with the membrane, said actuator having a plurality of actuating portions thereon,   electrical contact means,   and a plurality of electromechanical control means each of which is movable with snap action to engage or disengage said electrical contact means to perform a selected control function in response to the application of predetermined force thereto and each of which resiliently resists such movement with a predetermined force, said control means normally engaging the respective actuating portions of the actuator so they cooperate in resiliently resisting movement of the membrane and actuator in response to pressure applied to the membrane but so that respective different numbers of said control means are permitted to move to perform their control functions in response to the application of selected different levels of pressure to the membrane.   
     
     
       2. A pressure sensing device having a plurality of thresholds of response comprising a base,   a plurality of pairs of electrical contacts mounted in spaced relation on the base,   a membrane movable relative to the base in response to pressure applied thereto,   an actuator movable with the membrane, said actuator having a plurality of actuating portions thereon,   and a plurality of resilient curved disks which are actuable to change direction of curvature with snap action in response to the application of respective different predetermined forces thereto and which are adapted to resiliently resist such change of curvature with said respective different predetermined forces, said disks being arranged for opening and closing connection between respective pairs of said electrical contacts as said disks change said curvature, said disks being normally engaged with said respective actuating portions of the actuator so that the disks cooperate in resiliently resisting movement of the membrane and actuator in response to pressure applied to the membrane but so that respective different numbers of said disks move with snap action to change their curvature in response to the application of selected different levels of pressure to the membrane.   
     
     
       3. A pressure sensing device as set forth in claim 2 wherein said pairs of electrical contacts are disposed in a common plane on said base, said actuator is secured to the membrane for movement therewith, and said actuator has a plurality of actuating fingers having said respective actuating portions thereon exerting isostatic forces on the respective disks. 
     
     
       4. A pressure sensing device as set forth in claim 2 wherein said respective pairs of contacts are connected in series relation in a circuit and said disks are supported relative to said respective pairs of electrical contacts for normally closing connection between the respective pairs of contacts and for opening said connection when said disks are actuated to change their direction of curvature in response to application of pressure to the membrane, said device having selected resistances connected across the respective pairs of contacts for significantly increasing circuit resistance when the respective disks are actuated.